Titanium base alloys



Jan. 28, 1958 R. I. JAFFEE ETAL 2,821,475

TITANIUM BASE ALLOYS Filed Jan. 24, 1957 0 bx DE vPum EORDQO XOQ Q O J Eek huikb Mhkokhmg 02G .wwSOI M2? 025x 2 i uv o. n s & u 0

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1 i U mg M W m 5 RC E m I nited States Patent TITANIUM BASE ALLOYS Robert I. Jatfee, Worthington, and Horace R. Ogden, Columbus, Ohio, assignors, by mesne assignments, to Rem-Cru Titanium, Iuc., Midland, Pa., a corporation of Pennsylvania Application January 24, 1957, Serial No. 636,212

8 Claims. (Cl. 75175.5)

This invention pertains to strong and ductile titaniumbase alloys containing as essential constituents, aluminum and molybdenum.

In our Patent No. 2,554,031 we have disclosed a series of strong and ductile Ti-Al-Mo alloys containing 2.58% aluminum, 0.5-8% molybdenum, balance substantially titanium, to which may be added small and controlled additions of the interstitials, i. e., carbon up to 0.3%, oxygen and nitrogen up to 0.15% each, for increased strength without undue embrittlement.

As a result of our furfl'ier investigation, we have now discovered a new series of Ti-Al Mo alloys containing much higher molybdenum contents than our said patent, which likewise possess the desired properties of good tensile strength and adequate ductility for fabrication purposes, i. e., forging, rolling, etc.,' and which possess additional advantageous properties as discussed below. This new series of alloys according to the present invention are the titanium-base alloys containing about 0.5 to 8% aluminum and from more than 8 to about 40% molybdenum. A preferred range is about 1 to 8% aluminum and about to 20% molybdenum.

As is known, pure titanium metal has, at normal or 2,821,475 Patented Jan. 28, 1958 atmospheric temperatures a close-packed hexagonal or,

alpha microstructure which transforms at 885 C. to a body-centered cubic or beta microstructure. Aluminum is a promoter or stabilizer of alpha titanium. Molybdenum, on the other hand, is a promoter or stabilizer of beta titanium and is, moreover, beta-isomorphous with titanium.

The alloys of our patent aforesaid possess a mixed alpha-beta structure owing to the relatively low range of the molybdenum addition; whereas the alloys of the present invention in general possess a substantially allbeta structure as quenched from above the beta transus, owing to the much higher range over which the beta promoter, molybdenum, is present.

The alloys of the present invention containing up to about 15% molybdenum, as solution treated by soaking at a temperature above the beta transus and thereupon rapidly cooling or quenching, as in water, are in general characterized by a relatively low yield strength and a high ratio of ultimate to yield strength. In this condition they may be easily fabricated as by forging, rolling, extruding or otherwise plastically deforming. After thus fabricating to finished shape, they may be strengthened by aging at about 300-650 300550 C.

These alloys being predominantly of the untable beta type, i. e., substantially all-beta as quenched from above the beta transus, work harden very little and typically have excellent bend ductilities. Their tensile elongations tend to decrease as the ratio of aluminum to molybdenum present is increased. Hence the best tensile elongations are obtained by decreasing the aluminum content as themolybdenum content is increased. 7

The mechanical properties of typical alloys according to the invention in the as rolled and annealed condition or in the as rolled and solution treated condition," i. e., quenched from the beta field, are given in the following Table I: a

Table I Composition, Tensile Properties: Percent (Balance p. s. 1. 1,000 MBR um) Percent Percent Vickers Condition 1 Elonga- Reduction Hardness tion in 1" Area Al M0 0.2% Ofi- Ultimate L T set Yield Strength (COMMERCIAL PURITY TITANIUM BASE) 1 8 82 124 15 3B 297 ,1.0 1 10 73 110 18 29 321 1. 6 1 12 82 110 29 4-0 286 0. 9 1 12 141 144 5 26 t... 1 12 64 101 34 a 2 8 74 127 17 36 325 2. 4 2 10 123 13 20 3l7 1.2 2 12 64 106 14 41 283 0. 2 2 20 128 130 6 15 320 0. S 4. 4 2 24 126 127 9 22 323 0. 4 4. 0 3 8 126 13 29 301 l. 3 3 10 72 130 10 22 291 1.0 3 12 51. 121 13 21 302 l. 3

(IODIDE TITANIUM BASE) R and. A, 24 40 53 54 102 0 0 5 R and A, 62 79 17 41 268 5 RandA 102 125 7 24 293 5 10 R, 850 (5. 46 136 9 11 265 1. 5 5 12 R, 850 C. 87 132 5 i 7 288 0.7 5 14- R, 850 C. 105 16 30 272 0 5 15 R and A, 139 6 25 317 1 R=rolled, A=annealed, Q=solution treated at indicated temperature and quenched.

C., preferably about Table Icontinued Composition, Tensile Properties: Percent (Balance p. s. i. 1,000 MBR Titanium) Percent Percent Vickers Condition Elonga- Reduction Hardness tion in 1 in Area Al M 0.2% Oil'- Ultimate L '1 set Yield Strength (COMMERCIAL PURITY TITANIUM BASE) R 53 i 77 22 50 202 0.7 1.8 5 R, 96 108 22 37 342 2. 0 1. 5 5 R 141 153 5 18 363 5 10 R, 850 302 0 0. 7 5 12. 5 R, 850 298 2. 5 1.3 5 R, 850 109 110 6 37 285 0 5 17. 5 R, 850 295 0 0 0. 5 1 30 R, 760 130 130 11 30 284 0 0. 9 2 39 R, 980 123 128 3 13 298 3.0 3. 0 2 35 R, 980 31o 0. 5 40 11,980 l 337 I Annealed 14 hour at 840 C. and quenched.

As shown by the above data, the alloys containing up to about 15% molybdenum, have in the beta quenched condition, extremely low yield strengths, in general well under 100,000 p. s. 1., although their ultimate strengths as thus treated are relatively high. In this condition these alloys are accordingly susceptible to forming operations with relative case. They are also characterized by excellent response to aging after the aforesaid solution treatment, and may thus, either before or after forming, be greatly strengthened by aging. For these alloys, solution treating may be effected at upwards of about 650 C. to about 1000 C. Subsequent aging is carried out at about 300 to 650 C.

The accompanying drawing shows the aging response curves for specimens of the Ti-5Al-l5Mo alloy as solution treated at 950 C. and thereafter aged at 650, 700 and 750 C., respectively. Table II below compares the hardness and tensile properties for this alloy as solution treated and after the several aging treatments indicated. A similar comparison is also included for the Ti-lAl-12Mo The foregoing data establishes that, because of the excellent bend ductility and moderate strength for these alloys in the solution treated condition and their potent hardening on aging, these alloys are particularly suited for age hardening applications.

The alloys of tthe invention are further strengthened without embrittlement and with retention of adequate ductility for fabrication by interstitial additions up to a total of about 0.5%, but not to exceed about 0.3% for carbon, and 0.15% each for oxygen and nitrogen.

The alloys of the invention may be made by melt casting in a cold mold furnace employing an arc electrode in an inert atmosphere, or by equivalent procedures. Where the alloys of the invention are to be used for sheet material, the minimum bend ductilities may range as high as 201, and where used in massive form, as in forgings, the percent tensile elongation may range as low as 1 to 2%.

This application is a continuation-in-part of our copending applications Serial No. 381,442, filed September 21, 1953, now abandoned, and Serial No. 400,730, filed alloy. December 18, 1953 now abandoned.

Table II Composition, Tensile Properties: Percent (Balp. s. i. 1,000 once Titanium) Percent Percent Condition Elonga- Redue- Vickers tionin 1" tion in Hardness 0.2% Ultimate Area Al Mo Ofiset Strength Yield 5 15 950 C. Q 109 110 5 37 285 5 15 950 C. Q+8 hrs. at 500 C 186 8 502 5 15 950 C. Q+16 hrs. at 650 0... 142 144 1 387 5 l5 950 C. Q+16 hrs. at 650 C.+100 146 150 1 434 hrs. at 540 C. 1 12 780 C. Q 87 103 9 8 1 12 780 C. Q+24 hrs. at 510 C- 180 191 2 13 Table III shows hardness and bend ductility values for various other Ti-Al-Mo alloys after solution treating and aging, and after solution treating, cold working and 6 What is claimed is:

1. An alloy consisting essentially of: about 0.5 to 8% 0 aluminum, 10 to 40% molybdenum, up to a total of about 0.5% for carbon, oxygen and nitrogen, but not to exceed about 0.3% for carbon and 0.15% each for oxygen and nitrogen, balance substantially titanium, characterized in having as beta-quenched, a substantially all-beta microstructure, a tensile strength of at least 100,000 p. s. i., a tensile elongation of at least 2%, and a bend ductility of not over 20T.

2. A11 alloy consisting essentially of: about 0.5 to 8% aluminum, 10 to 20% molybdenum, balance substantially titanium, characterized in having as solution treated and quenched from a temperature in the range of about 650-1000 C., a relatively low yield strength, and of thereafter undergoing marked strengthening on aging at about 300-650 C.

3. An alloy containing about: 2.5 to 8% aluminum,

10 to 20% molybdenum, and the balance substantially titanium, characterized in being age hardenable to at least 350 Vickers by solution treating at upwards of about 650 C. followed by aging at about 300 to 650 C.

4. An age-hardened titanium-base alloy containing about: 2.5 to 8% aluminum and 10 to 20% molybdenum, balance substantially titanium, characterized in having a Vickers hardness of at least 350.

5. An alloy containing about: 0.5 to 8% aluminum, 10 to 40% molybdenum, and the balance substantially titanium, characterized in being age hardenable to at least 350 Vickers on solution treating at upwards of 650 C. followed by aging at about 300 to 650 C., and in having in the age hardened condition a minimum bend ductility of not over 20T.

6 0.5 to 8% aluminum and 10 to 40% molybdenum, characterized in having an ultimate strength of at least 100,000 p. s. i. and a tensile elongation of at least 5%.

8. An alloy containing about: 0.5 to 8% aluminum, 10 to 40% molybdenum and the balance substantially 10 titanium, characterized in having an ultimate strength of at least 100,000 p. s. i. and a tensile elongation of at least 5%. i

No references cited. 

1. AN ALLOY CONSISTING ESSENTIALLY OF: ABOUT 0.5 TO 8% ALUMINUM, 10 TO 40% MOLYBDENUM, UP TO A TOTAL OF ABOUT 0.5% FOR CARBON, OXYGEN AND NITROGEN, BUT NOT TO EXCEED ABOUT 0.3% FOR CARBON AND 0.15% EACH FOR OXYGEN AND NITROGEN, BALANCE SUBSTANTIALLY TITANIUM, CHARACTERIZED IN HAVING BETA-QUENCHED, A SUBSTANTIALLY ALL-BETA MICROSTRUCTURE, A TENSILE STRENGTH OF AT LEAST 100,00 P.S.I., A TENSILE ELONGATION OF AT LEAST 2%, AND A BEND DUCTILITY OF NOT OVER 20T. 